U.S. patent number 3,801,114 [Application Number 05/295,964] was granted by the patent office on 1974-04-02 for hydrodynamic shaft seal of the type having a series of flat annular washers.
This patent grant is currently assigned to Federal-Mogul Corporation. Invention is credited to Gustavus A. Bentley.
United States Patent |
3,801,114 |
Bentley |
April 2, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
HYDRODYNAMIC SHAFT SEAL OF THE TYPE HAVING A SERIES OF FLAT ANNULAR
WASHERS
Abstract
Three resilient annular washers, such as
polytetrafluoroethylene, are clamped into a metal case, either
before or after they have been pre-formed to provide substantially
frustoconical inner portions, the inner peripheries of the
pre-formed washers being substantially smaller than the outer
periphery of the shaft they are to engage. The first and third
washers, one on the oil side of the seal and the other on the air
side, respectively, have circular inner peripheries, at least the
first washer providing a static seal against the shaft. A second
washer, in between the other two washers, provides a non-circular
inner periphery with some portions out of contact with the shaft.
Pressures and pressure gradients causing hydrodynamic action are
generated in the oil film at normal shaft speeds, as a result of
the motion of the oil caused by adhesion to the rotating shaft
through constantly changing spaces.
Inventors: |
Bentley; Gustavus A. (Ann
Arbor, MI) |
Assignee: |
Federal-Mogul Corporation
(Southfield, MI)
|
Family
ID: |
23139987 |
Appl.
No.: |
05/295,964 |
Filed: |
October 10, 1972 |
Current U.S.
Class: |
277/559; 277/562;
277/570; 277/577 |
Current CPC
Class: |
F16J
15/3244 (20130101); F16J 15/3228 (20130101) |
Current International
Class: |
F16J
15/32 (20060101); F16j 015/32 (); F16j
015/40 () |
Field of
Search: |
;277/133,134,51 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Prince; Louis R.
Assistant Examiner: Smith; Robert I.
Attorney, Agent or Firm: Owen, Wickersham & Erickson
Claims
I claim:
1. A shaft seal of the type having a metal case and washer-type
resilient sealing means, the seal being characterized by being
capable of hydrodynamic oil-returning action and comprising:
a cylindrical bore-engaging portion,
three resilient annular washers, each having a radially inner
frustoconical portion with a shaft-contacting edge portion and
having a radially outer flat portion, said washers having their
inner diameters substantially smaller than the diameter of the
shaft they are to engage,
a first said washer on the oil side of said seal having a circular
inner periphery providing a static seal against the shaft,
a second said washer next to said first washer and having an inner
periphery provided with a portion well out of contact with said
shaft and portions continuously approaching contact with the shaft,
and
a third said washer on the air side of said seal and having a
circular inner periphery.
2. The shaft seal of claim 1 wherein the inner periphery of the
third said washer is continuously circular for continuous shaft
contact.
3. The shaft seal of claim 1 wherein the inner periphery of the
third said washer is provided with passages for admitting air and
oil into the space between said third washer and said first
washer.
4. The shaft seal of claim 3 wherein said second washer has an
elliptical periphery and wherein there are two said openings
through said third washer located in rotational positions close to
the extremities of the major axis of said elliptical periphery.
5. The shaft seal of claim 4 wherein said openings are located
exactly axially in line with the extremities of said major axis,
for optimal bidirectional hydrodynamic action.
6. The shaft seal of claim 4 wherein said openings are rotationally
displaced somewhat from the extremities of said major axis, in the
direction contour to the direction of shaft rotation, for optimal
unidirectional hydrodynamic action.
7. The shaft seal of claim 1 wherein said second washer is
elliptical with both extremities of the major axis thereof equally
out of contact with the shaft.
8. The shaft seal of claim 1 wherein said second washer is circular
and is located eccentrically with respect to the other two
washers.
9. The shaft seal of claim 1 wherein said second washer has a wavy
periphery with at least three portions spaced at an extreme
distance from the shaft.
10. The shaft seal of claim 1 wherein said washers are
polytetrafluoroethylene.
11. A shaft seal of the type having washer-type resilient sealing
means and capable of hydrodynamic oil-returning action,
comprising:
a metal case having a cylindrical bore-engaging portion and a
radial flange,
three resilient annular washers, each having a radially inner
frustoconical portion with a shaft-contacting edge portion and
having a radially outer flat portion,
clamping means forcing the outer portions of said washers toward
said flange, to hold them in place and to prevent leakage between
them and the case,
said washers having their inner diameters substantially smaller
than the diameter of the shaft they are to engage,
said seal being characterized by said three washers comprising:
a first said washer on the oil side of said seal having a circular
inner periphery providing a static seal against the shaft,
a second said washer next to said first washer and having an inner
periphery providing at least one portion well out of contact with
the shaft and smoothly and continuously joined to at least one
portion in contact with said shaft, providing differences in fluid
pressure as said shaft rotates, building up at the portion in
contact with the shaft higher pressures in the space between its
inner periphery and that of said first washer, the pressure being
lower at the portion well out of contact with the shaft, and
a third said washer on the air side of said seal and having a
circular inner periphery.
12. The shaft seal of claim 11 wherein said third washer has a
continuous circular periphery.
13. The shaft seal of claim 11 wherein said third washer is
provided with openings adjacent the portions of the second said
washer well out of contact with said shaft, for admitting air and
oil into the space between said third washer and said first
washer.
14. The shaft seal of claim 11 wherein said washers are
polytetrafluoroethylene.
Description
BACKGROUND OF THE INVENTION
This invention relates to a shaft seal of the type having
washer-type resilient sealing members, and the invention is
particularly directed to making such seals hydrodynamic
oil-returning devices.
The invention is especially applicable to types of materials such
as polytetrafluoroethylene where it is impractical to make seals by
molding a resilient thermosetting elastomeric material into a
complex shape. While polytetrafluoroethylene and similar materials
can be shaped by various methods, they present a different problem
from such materials as butadiene styrene or acrylic elastomers, and
so on. Yet they may have very valuable properties -- abilities to
seal liquids that react with or corrode ordinary seal components,
ability to withstand extreme temperatures and ability to operate
under greater-than-atmospheric pressures.
Few polytetrafluoroethylene elastomeric shaft seals have performed
satisfactorily, because of the relative stiffness of
polytetrafluoroethylene as compared with the synthetic rubbers and
because of its inability to maintain intimate contact across
asperities of the shaft surface. Materials like
polytetrafluoroethylene can be used most economically when they are
sliced from tubular billets, and this has led to the development of
multilip seals, but it was still difficult to obtain hydrodynamic
action from them. By this is meant the type of action in which the
oil which has leaked past the seal is returned back to the oil side
of the seal. Such leaks do not necessarily reflect upon the
efficiency of the sealing member itself, but they may be caused by
grooves, scratches, or other defects in the shaft upon which the
seal makes contact. When there are such grooves or scratches and
when oil is able to follow them out beneath the seal, then (unless
hydrodynamic action can be obtained) there is leakage, and this may
be serious. However, with hydrodynamic action there is no true
leakage, since the oil can be returned.
Therefore, many seal users, particularly automobile manufacturers
and manufacturers of other automotive equipment have been demanding
that shaft seals possess hydrodynamic action, so that whether the
seal itself is substantially perfect, it may in addition overcome
the factors that tend to cause leakage through no fault of such
seals.
The ribs, grooves and other structures that have been used in
attempts to provide hydrodynamic action with most elastomeric seals
are difficult to apply effectively to polytetrafluoroethylene
washers, and the expense of applying them has frequently been far
too great to justify doing so.
SUMMARY OF THE INVENTION
This invention applies to all shaft seals of the washer type, and
is not limited to polytetrafluoroethylene as a material.
Three resilient annular washers are clamped into a metal case.
Either before or after clamping, these washers are pre-formed to
provide an inner frustoconical portion. The inner diameters of the
preformed washers are substantially smaller than the diameter of
the shaft they are to engage. In this invention the middle washer
differs from the others. A first washer, which is on the oil side
of the seal, is provided with a circular inner periphery. In some
forms of the invention it gives a static seal upon contact with a
shaft; in other forms of the invention the footprint of this washer
is interrupted at the minor diameter of the middle element. This
first washer does the valving for the hydrodynamic action, for the
three lips cooperate to provide hydrodynamic action which returns
the oil back into the main oil reservoir.
The second washer, which is the middle one and is next to the first
washer, has an inner periphery that is non-circular; it may be
eccentric or elliptical or wavy or irregular. If ellipitcal, for
example, the second washer has at opposite ends of its major axis
two portions that are out of contact with the shaft. At each end of
the minor axis, the second washer is in actual contact with the
shaft. This structure results, upon rotation of the shaft, in
differences of pressure in the changing volume of the space between
the third washer and the first washer. The pressure is greatest at
the minor axis and tends at that point to return oil beneath the
first washer to the oil reservoir. If the inner periphery of this
second washer is circular but located eccentrically with respect to
the axis of the shaft there is one point of good contact and one
point with maximum distance from the shaft, and the basic operation
is similar. If the middle element or second washer is wavy or
irregular instead of elliptical, then there may be more than two
points corresponding to the points at the ends of the major axis
and more than two points corresponding to the points at the ends of
the minor axis of the ellipse, but the general configuration is
quite similar, as will be seen later from the drawings, and so is
the operation.
The third washer is on the air side of the seal and may have a
circular inner periphery; it may be exactly like the first washer,
and in that instance this third washer provides the static seal; or
it may differ (in some forms) by being provided with openings,
which may be recessed portions of the periphery, to let air into
the space between the third washer and the second washer, and in
that instance, the first washer must provide the static seal. If
such openings are desired, then, depending on whether the seal is
to be unidirectionally or bidirectionally hydrodynamic, these
openings are located in certain positions, later to be discussed,
relative to the major axis or points of the periphery most distant
from the shaft of the second washer. These openings let air (or
oil) come in, so that the seal is assured of having atmospheric
pressure at certain points, and then the pressure can build up in
the irregularly shaped space lying between the first and second
lips and the shaft, so as to force the hydrodynamic action. In
practice, it has been found that such a seal with openings very
well pumps oil that is placed on the shaft just outside the third
washer right into the oil reservoir, passing beneath all three of
the lips to get there. Where such pumping is not desired, the
openings are not provided.
By way of analogy or comparison, a parallel may be drawn between
the triple lip seal of this invention and a hydraulic radial piston
pump. In the case of the seal of this invention, the continuously
changing void caused by the elliptical or wavy configuration of the
middle washer or middle lip provides a constantly changing
cross-sectional area, which resembles the effect of the motion of
the pistons in a pump cylinder. As oil is moved around this space
of changing volume by the rotating shaft, the oil is alternately
squeezed in the small cross-sectional areas and is subjected to a
negative pressure or partial vacuum as it progresses to an area of
larger cross section. The two outside lips may act somewhat like
reed or flapper check valves, or, as noted, the air-side lip may
have openings to let air or oil come in at certain locations. The
lips are so oriented and so shaped that the oil can flow only from
the air side of the seal to the oil side of the seal. Any pressure
in the opposite direction tends to push the lips into more intimate
contact with the shaft and to shut off the flow of oil from the oil
side to the air side.
When a simple ellipse is used as the inner periphery of the middle
lip, there are two diametrically opposite high pressure areas and
two diametrically opposite low pressure areas located 90.degree. on
either side of the high pressure areas. As the oil progresses
through these, a first high pressure region pushes the first and
third lips so that they tend to move apart from each other. Because
of the angle of approach to the shaft of these lips, the lip on the
air side tends to be pushed against the shaft, while the lip on the
oil side tends to be lifted from the shaft, so that oil on the air
side of the oil-side lip is placed under pressure and thereby
caused to flow toward the oil side, lifting the oil-side lip.
Ninety degrees later, the outside lips are subjected to reduced
pressures so that they tend to collapse toward each other. This
action pulls the oil-side lip against the shaft at the same time
that the air-side lip is pulled away from the shaft, except when
there are openings in the air-side lip, which actually admit air or
oil into the space between the two outside lips. Any oil on the air
side thus tends to move into the region of low pressure between the
outside lips. Another 90.degree. later, this oil is pressurized and
continues to move toward the oil side of the seal as described
before. The process is continuous so long as the shaft is turning.
When the seal is at rest, the oil-side lip forms a static seal when
the air-side lip has openings or interruptions in shaft contact,
and if the air-side lip has no openings or interruptions in shaft
contact, it provides the static seal, while the oil-side lip then
has interruptions in its shaft contact.
An advantage of the invention is that it makes possible the
production of hydrodynamic seals from materials that are less
easily elastic than conventional lip seal elastomers. For instance,
as already mentioned, polytetrafluoroetylene, which is
comparatively rigid, is an ideal material for making long-wearing
seals that can withstand operation in fluids at temperatures up to
600.degree. F. However, polytetrafluoroethylene seals have been
unreliable and have had a tendency to leak, unless they can be made
hydrodynamic, as they can by this invention.
Other objects and advantages of the invention will appear from the
following description of some preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a view in end elevation looking from the air side of a
triple lip seal embodying the principles of the invention and
providing bidirectional hydrodynamic action.
FIG. 2 is a greatly enlarged view in section taken along the line
2--2 in FIG. 1.
FIG. 3 is a view similar to FIG. 1 of a modified form of the
invention employing a center lip that has an eccentrically located
circular lip edge.
FIGS. 4 and 5 are diagrams indicating the hydrodynamic action of
the seal of FIGS. 1 and 2 in both the clockwise shaft rotation
(FIG. 4) and counterclockwise shaft rotation (FIG. 5).
FIG. 6 is a view similar to FIG. 1 of a modified form of invention
where the air-side lip has two openings diametrically opposite
along a line that is displaced relatively to the major axis of the
middle lip, so as to give hydrodynamic action biased toward the
direction of rotation shown by the arrows.
FIG. 7 is a view similar to FIG. 6 with the displacement on the
opposite side to give unidirectional action in the opposite
direction of rotation, as shown by the arrows.
FIG. 8 is a view similar to FIG. 1 of a modified form of seal in
which, instead of having an elliptical middle lip, this lip is
provided with a wavy periphery; while the air-side lip has openings
at locations substantially opposite the points of greatest distance
of the periphery of the middle lip from the shaft, thereby giving
bidirectional hydrodynamic action.
FIG. 9 is a greatly enlarged view in section, taken along the line
9--9 in FIG. 8 showing a particular lip shape for the seals at
their inner periphery.
FIG. 10 is a similar view in section taken along the line 10--10 in
FIG. 8.
FIG. 11 is a view similar to FIG. 1 with the eccentricity of the
ellipse somewhat exaggerated and with two diametrically opposite
openings through the air-side lip located for bidirectional
hydrodynamic action.
FIG. 12 is a view setting forth diagrammatically the proximity of
the inner periphery of the middle lip to the shaft relative to the
position of shaft rotation for the device of FIG. 11.
FIG. 13 is a view aligned with FIG. 12 showing the pressure
variation consequent upon the proximity of the middle lip of the
shaft, with fluid film pressure versus shaft rotation.
FIG. 14 is also aligned with FIGS. 12 and 13 and shows
diagrammatically a flow pattern as a result of pressure variation
corresponding to the shaft rotation and fluid pressure, with the
points of opening through the air side shaft being indicated
also.
DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS
FIGS. 1 and 2 show one preferred embodiment of this invention,
namely, a hydrodynamic oil seal 20 for use on a rotating shaft 21
and designed to seal between the shaft 21 and a cylindrical bore
22. The oil seal 20 has a housing or outer case 23, preferably of
metal, having a cylindrical bore-engaging portion 24 and a radially
extending flange 25.
A gasket 26 may abut the inner surface of the flange 25, and an
inner case 27 has a flange 28 and a cylindrical portion 29 nesting
in the portion 24 of the outer case 23. The outer case 23 may have
a curled-over portion 30 to hold the inner case 27 in place and to
clamp three resilient washers 31, 32, and 33 toward the radial
flange 25 and against the gasket 26, which seals against leakage
there.
The sealing washers 31, 32, and 33 may be of
polytetrafluoroethylene or may be made of plastic, elastomer, or
some other kind of suitable material, and they are preferably made
by cutting out annular slices from a round billet or tube or by
cutting out annular pieces from flat sheets, although they can be
made by fabricating individual washers from polytetrafluoroethylene
powder. Each of these washers 31, 32, 33 is preformed, either
before or after it is assembled into the case 23, so that it has a
radially inner frustoconical portion and a flat outer portion. The
three members 31, 32, and 33 shown may have slightly different
basic inner peripheries 41, 42, 43 to make up the angle of bending,
so that the oil-side member 31 may have the smallest inner
periphery and the air-side member the largest. The frustoconical
inner portions 44, 45, and 46 of these washers 31, 32, and 33 are
able to flex, while the outer clamped portions 47, 48, and 49 are
held between the two clamping members 25 and 28. The inner
peripheries 41, 42, 43 of the seals may be ground, if desired, to
make the form of lip shown in FIGS. 9 and 10, or they may be simply
cut straight across when the washers are flat, as shown in FIG. 2.
In this event, one corner of the oil-side lip 31 provides its
sealing edge.
While the sealing edge or inner peripheries 41 and 43 of the
oil-side washer 31 and air side washer 33 are circular, the inner
periphery 42 of the middle lip or second washer 32 is, in this
instance, a true ellipse. There need not be a very large difference
between the major and minor diameters. For example, seals three
inches across have had the major axis greater than the minor axis
by 0.010 inch in some instances, by 0.020 inch in others, by 0.040
inch in other, and by 0.060 inch in still others, and all four
dimensions gave satisfactory results. The smaller diametrical
differences give higher ultimate internal pressures with decreased
flow volume, due to shear force in the fluid film. Other dimensions
are, of course, possible. At the major axis 50, the seal of FIGS. 1
and 2 is well out of contact with the shaft 21, while at the minor
axis 51, it is, in this instance, in actual contact with the shaft
21. This is not always necessary, but is preferable. The minor axis
may still have the lip somewhat retracted from the shaft, but by a
smaller enough amount than that of the major axis to give the
desired result. However, there are some advantages in having actual
contact at this point. There is, thus, a chamber 52 between the
inner portions of the first and second lips 31 and 32, and there is
another chamber 53 between the second and third lips 32 and 33.
However, due to the fact that the middle lip 32 is elliptical,
these two chambers are joined together at the ends of the major
axis 50 of the ellipse (see FIG. 1).
FIGS. 4 and 5 show how the seal 20 of FIGS. 1 and 2 provides
hydrodynamic action. The lips 31, 32, and 33 are shown in solid
lines where they contact the shaft 21 and the lips 31 and 32 are
shown in broken lines where they do not touch the shaft 21 during
rotation of the shaft at the times there is hydrodynamic action.
FIG. 4 relates to clockwise rotation of the shaft 21 and FIG. 5 to
counterclockwise rotation of the shaft 21. The dotted-line portions
for the lip 32 indicate the portions where the elliptical shape
avoids shaft contact, the width of the solid lines for all lips
illustrates the degree of contact, and the curving or sinuous path
of the middle lip 32 indicates a development of the ellipse, not
the actual projection of the lip 32. The lip 31 is in actual
contact with the shaft except at locations where the pressure in
the space between the lips 31 and 33 is such as to force the lip 31
to lift enough to force back to the oil side thereof any oil in the
space near the lip 31, and this pressure prevents oil from leaking
past the lip 31 from its oil side. The views are, of course,
diagrammatic. The heavy continuous contact pattern of the lip 33
shows how that lip acts as a static seal.
FIG. 3 shows a seal 35 that is basically similar to the seal 20,
except that the middle lip 36, in between the lips 31 and 33 is
circular, with its circle offset from or eccentric to the axis of
the shaft 21. The results are similar to those of the seal 20, but
there are only half as many low-pressure zones, half as many
high-pressure zones, and only one area (instead of two) where the
oil can be returned to the oil side of the lip 31 by lifting that
lip.
In FIG. 11, the air-side lip 33a has a circular inner periphery 43a
in which openings 54 and 55 are provided, as by recesses in this
periphery 43a. The openings 54 and 55 through the air-side lip 33a
admit air freely into the chamber 53 (FIG. 2) between the second
and third lips 32 and 33a, and since at these points the chamber 52
between the first and second lips 31 and 32 is also open, the
openings 54 and 55 admit air into the chamber 52 (FIG. 2) too. As
shown in FIG. 11, to obtain bidirectional hydrodynamic action, the
openings 54 and 55 coincide in rotational position with the major
axis of the elliptical middle lip 32.
As shown in FIGS. 6 and 7, these openings 54 and 55 may be replaced
by openings 56 and 57 or 58 and 59 displaced from the major axes,
when a unidirectional hydrodynamic action is more satisfactory. In
other words, if the shaft is never going to rotate except in one
direction, then advantage can be taken of that fact to obtain
increased pumping action by displacing the openings through the
third lip 33b or 33c so that they are rotationally ahead of the
major axis 50 of the second lip 32. As shown in FIGS. 6 and 7, this
may be about 45.degree. ahead. Depending on actual shaft speed, the
rotational positions may be varied in these instances.
The seals of FIGS. 1-3, 6-8, and 11 all prevent leakage, such as
that induced by a standard rolled-groove mandrel, which is a
rotating shaft with a spiral 90.degree. V-shaped helical groove
0.003 inch deep and having a helix angle of 4.degree.. The seals of
FIGS. 6, 7, 8, and 11 will pump and will transfer fluid from the
outside of the air-side lip 33a, 33b or 33c to the oil side of the
oil-side lip 31, but the seals of FIGS. 1-3 will not do this. Both
types of structure have their advantages and disadvantages.
For example. for an installation at the front crank position of an
engine, the seals of FIGS. 1-3 are preferred becasue they will
exclude moisture and contaminants that lie outside the air-side lip
33, blocking them out while also blocking in the flow of oil,
whereas the seals of FIGS. 6, 7, 8, and 11 would tend to pump them
into the crankcase. Also, the seals of FIGS. 1-3 are more easily
assembled, for there is no necessity for orientation of the ports
through the lips 33a, 33b, and 33c. In effect, the middle element
32 of the seal of FIGS. 1 and 2 acts very much like the flutes of a
hydrodynamic seal of conventional design, except that the
decreasing volume cavity into which the oil is squeezed is radial
in the present seal rather than axial as in the conventional
design.
Moreover, the continuous flow of the fluid film away from the
air-side element toward and beyond the oil side element, leaves an
area of negative pressure between the air-side lip 33 and the
middle lip 32, as has been observed in high speed photomicrographs.
The pumping action of a rolled-groove mandrel is ineffective in
this region, where fluid flow is blocked by a continuous
low-pressure zone, so that there can be no leakage beyond the
air-side lip 33 unless oil first fills this low-pressure zone.
In the seal 20 of FIG. 1, there are two diametrically opposite high
pressure areas and two diametrically opposite low pressure areas.
The high-pressure areas are at the minor axis 51 and the low
pressure at the major axis 50. So long as the seal is not leaking
at all and no oil has passed the air-side lip 33, the air-side lip
33 acts as the seal, both statically and dynamically, that prevents
the passage of oil. The lips 32 and 33 reinforce the lip 31
somewhat and give it a little stiffness. If the shaft 21 should be
scratched or there should be some minor defect in either the shaft
21 or the seal 20 which permits the passage of some oil beyond the
oil-side of the oil-side lip 31, then oil enters the chamber 52.
Also, the minor diameter of the lip 32 forces the lip 31 off the
shaft twice for each revolution of the shaft. In each high pressure
region, pressure is exerted on the oil and it tends to be squeezed,
while in the low pressure areas, air tends to enter to minimize the
flow of oil in the opposite direction. Thus, oil on the air side
tends to move into the region of low pressure between the outside
lips 31 and 33, and then 90.degree. later the oil is pressurized
and continues to move toward the oil side of the seal. At the
points where the lip 31 on the oil side is lifted from the shaft
21, this pressure forces the oil back in to the reservoir, and the
pressure itself also prevents oil from the oil side from leaking
out. At the other point, in the low pressure areas, the oil-side
lip 31 is forced firmly against the shaft 21 and therefore does not
permit the passage of oil at those times.
FIG. 8 shows a seal 60 generally like the seal of FIG. 11, having
three lips 61, 62, and 63, but the middle lip 62 has six points at
which the middle lip 62 is distant from the shaft 21 and six where
it is quite close to or against the shaft 21. The oil-side lip 61
is circular, and the air-side lip 63 has six openings 64, one at
each of the points where the middle lip 62 is most distant from the
shaft 21. This structure may be used in quite large sealing members
where it is felt that a simple ellipse would not be efficient
enough. However, the ellipse has been used in seals up to six
inches and has pumped very satisfactorily.
FIGS. 9 and 10 illustrate the distance of the middle lip 62 from
the shaft 21 with two different positions being shown in each view,
one in broken lines at 66 with actual contact and one in solid
lines 66a where the contact is barely made at the high pressure
position. Similarly, the distances at low pressure are shown. The
opening through the air side lip 63 is shown, and the sealing of
the inner lip 61 is shown. In this instance, the lips 61 and 63
have been ground, so that there is contact along the full width of
their respective peripheries 65, 67. The periphery 65 is raised out
of contact with the shaft because of pressure causing flow of oil
back under the periphery 65 to the oil side of the seal.
FIGS. 11 through 14 diagrammatically show what happens during
operation of the device having holes through the lip 33a. The
positions are noted on this diagram, and it will be seen that at
zero or 360.degree. is one of the points where the middle lip 32 is
close to or in actual contact with the shaft and that at 90.degree.
and 270.degree. the points of the major axis of the ellipse are
reached where the middle lip 32 is the furthest away from the
shaft. At 180.degree. the lip 32 is in the same position as it is
at zero and 360.degree.. The actual proximity of a particular
example is shown in FIG. 12 with the middle lip 32 being very close
to the shaft at zero, 180.degree. and 360.degree., diverging from
the shaft up to maximum at 90.degree. and 270.degree., and coming
back toward it again after 90.degree. and after 270.degree..
The consequent pressure variation is shown in FIG. 13, and it will
be seen that the fluid film pressure varies from positive to
negative relative to atmospheric along this path.
FIG. 14 then shows the flow pattern which results from the pressure
variation and illustrates also the location of the openings letting
air and fluid in. It will be seen that the flow tends to be away
from the air side lip and toward the middle lip and then from the
middle lip toward the inner lip and that there are always the two
patterns of the fluid tending to enter in that way.
To those skilled in the art to which this invention relates, many
changes in construction and widely differing embodiments and
applications of the invention will suggest themselves without
departing from the spirit and scope of the invention. The
disclosures and the description herein are purely illustrative and
are not intended to be in any sense limiting.
* * * * *